1. Field of the Invention
The present invention relates to a novel lubricating oil for refrigerators with a compressor. More particularly, it relates to a lubricating oil for refrigerators with a compressor (compression-type refrigerators), comprising as the main component a polyoxyalkyleneglycol derivative having a high lubricating property as well as a favorable compatibility with hydrogen-containing fluorocarbon compounds such as 1,1,1,2-tetrafluoroethane (hereinafter referred to as R-134a), which can substitute for Freon compounds such as dichlorodifluoromethane (hereinafter referred to as R-12) used as refrigerant and involved in environmental pollution problems.
2. Description of the Related Arts
Generally, a compression-type refrigerator is constituted of a compressor, a condenser, expansion bulbs, and an evaporator, having a mechanism where the mixture of the refrigerant and the lubricating oil is circulating in a closed system. In such a refrigerator, though it depends on the kind of apparatus, usually the temperature in the compressor rises to 40xc2x0 C. or more, while in the cooler, the temperature comes to be so low as xe2x88x9240xc2x0 C. Accordingly, the refrigerant and the lubricating oil must circulate in the said system without phase separation in the said temperature range of xe2x88x9240xc2x0 C. to +40xc2x0 C. in most cases.
If phase separation is caused while the running of the refrigerator, a seriously detrimental effect occurs affecting the life and efficiency of the apparatus. For example, if phase separation of the refrigerant and the lubricating oil is caused in the compressor, moving parts become underlubricated resulting in seizure or other troubles, which shorten the life of the apparatus considerably. If phase separation is caused in the evaporator, a lubricating oil having a high viscosity results, which brings lowering of efficiency in heat exchange.
Since a lubricating oil for refrigerators is used for the purpose of lubricating the moving parts of the refrigerator, its lubricating ability is regarded important as a matter of course. Particularly in the compressor, the temperature becomes so high that a viscosity, sufficient to retain the oil film necessary for lubricating, is important. Necessary viscosity varies with the kinds or running conditions of the compressor, but usually the preferable viscosity of the lubricating oil before blended with refrigerant is 2 to 250 cSt at 100xc2x0 C. If the viscosity is lower than that range, the oil film becomes thinner thereby causing underlubricating and sealing properties become poor, while if the viscosity is higher than the above, the efficiency in heat exchange is reduced. Since lubricating oils for refrigerator are used in circulation in a wide range of high to low temperatures, its viscosity index is preferably high, and usually a viscosity index of 40 or more is required. Further, in addition to the above properties, a low hygroscopicity to prevent the blocking of the bulb caused by icing at the expansion bulb and other properties are required.
Heretofore, as the refrigerant for compression-type refrigerators, R-12 has often been used, and as the lubricating oil, various mineral oils and synthetic oils satisfying the required properties mentioned before have been used. R-12, however, has recently been restricted more and more severely all over the world, for it is liable to cause environmental pollution including destruction of the ozonosphere.
In these circumstances, hydrogen-containing fluorocarbon compounds including R-134a have attracted attention, as new refrigerants. Among the hydrogen-containing fluorocarbon compounds, R-134a especially has only a small possibility of destroying the ozonosphere, and can substitute for R-12, with little change in structure of the conventional refrigerators, and accordingly is favorable as a refrigerant for compression-type refrigerators.
When the hydrogen-containing fluorocarbon compounds including said R-134a are employed as the refrigerant for compression-type refrigerators in place of R-12, the desirable lubricating oils come to be those having high compatibility with the hydrogen-containing fluorocarbon compounds including R-134a, and also having high lubricating properties enough to satisfy the required properties mentioned above.
However, since the conventional lubricating oils which have been used with R-12 do not have a favorable compatibility with the hydrogen-containing fluorocarbon compounds including R-134a, a new lubricating oil suitable to these compounds consequently is required. In that case, particularly in the air-conditioner for automobiles, it is required that the construction of the mechanism be hardly changed on the occasion of substituting for R-12. It is not desirable to change widely the construction of the present mechanism because of lubricating oil. Accordingly, a lubricating oil having a very favorable compatibility with the hydrogen-containing fluorocarbon compounds, including R-134a, is required.
As lubricating oils having compatibility with R-134a, Ulcon LB-165 or Ulcon LB-525 (Trade Mark, both produced by Union Carbide Co., Ltd.) composed of polyalkyleneglycol have been known, and it was reported that these lubricating oils are dissolved or compatible with R-134a in all proportions at a low temperature of xe2x88x9250xc2x0 C. or lower (xe2x80x9cResearch Disclosurexe2x80x9d, No. 17463 (October, 1978)). Moreover, a high viscosity refrigerator oil composition of which the base oil is poly-oxypropyleneglycolmonobutylether is known (Japanese Patent Publication No. 42119/1982). These lubricating oils are polyalkyleneglycol derivatives having polypropylene glycol with a hydroxyl group at one of the terminals and a n-butyl ether bond (a n-butoxy group) at the other terminal. They have a comparatively favorable compatibility with R-134a at low temperatures, but they do not have sufficient compatibility with R-134a at high temperatures, and for example, Ulcon LB-525 mentioned above is known to cause phase separation with R-134a at room temperature (Specification of U.S. Pat. No. 4,755,316).
On the other hand, a polyglycol having at least two hydroxyl groups in a molecule is proposed to be a favorable substance compatible with R-134a (Specification of U.S. Pat. No. 4,755,316).
In the said polyglycol, however, the.compatibility is not necessary sufficient.
Meanwhile, it is known that polyglycol generally shows a temperature dependency that when the mixture with a fluorocarbon or chlorofluorocarbon compound is heated from a low temperature to a high temperature, then the mixture phase-separated is once dissolved and phase-separated again.
On the other hand, R-134a and compounds which can dissolve it were proposed for use in absorption-type refrigerators (Japanese Patent Kokai No. 79175/1989). Said absorption-type refrigerators, however, are quite different in mechanism from the before-mentioned compression-type refrigerators, and tetraethylene-glycoldimethylether described in the Examples of the above-described Kokai is not proper as a lubricating oil for compression-type refrigerators because of its particularly low viscosity.
As described above, lubricating oil for compression-type refrigerators having sufficiently favorable compatibility with R-134a as well as high lubricating properties have not been found yet, and their development has been eagerly desired.
Replying to these requirements, the present inventors have earnestly studied to develop a lubricating oil suitable to compression-type refrigerators employing, as the refrigerant, hydrogen-containing fluorocarbon compounds including R-134a which are able to substitute for R-12 now involved in environmental pollution problems and other fluorocarbon compounds which are difficult to decompose.
The object of the present invention is to provide a lubricating oil for compression-type refrigerators, having a favorable compatibility with hydrogen-containing fluorocarbon compounds including R-134a as the refrigerant.
Another object of the present invention is to provide a lubricating oil for compression-type refrigerators, having a favorable compatibility with the above-described hydrogen-containing fluorocarbon compounds over the whole temperature range of application.
A further object of the present invention is to provide a lubricating oil for compression-type refrigerators, which has a favorable compatibility and also a high lubricating properties as described above.
A still further object of the present invention is to provide a lubricating oil for compression-type refrigerators, which has an excellent anti-seizure property in addition to the above-described properties.
The present invention comprises the following Lubricating Oil I to Lubricating Oil VII.
Lubricating Oil I
A lubricating oil for compression-type refrigerators, comprising, as the main component, at least one polyoxyalkyleneglycol derivatives represented by the general formula:
R1xe2x80x94[xe2x80x94(OR2)mxe2x80x94OR3]nxe2x80x83xe2x80x83(I)
wherein, R1 indicates an alkyl group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms or an aliphatic hydrocarbon group having 2 to 6 valencies, R2 is an alkylene group having 2 to 4 carbon atoms, R3 is an alkyl group having 1 to 10 carbon atoms, or an acyl group having 1 to 10 carbon atoms. n indicates an integer of 1 to 6, and m is an integer of 1 to 80.
Lubricating Oil II
A lubricating oil for compression-type refrigerators, comprising, as the main component, a polyoxyalkyleneglycol derivative represented by the general formula:
R4(OR5)kOHxe2x80x83xe2x80x83(I)
wherein R4 indicates an alkyl group having 1 to 3 carbon atoms, R5 indicates an alkylene group having 2 to 4 carbon atoms, and k indicates a number of 6 to 80.
Lubricating Oil III
A lubricating oil for compression-type refrigerators, comprising, as the main component, polyoxyalkyleneglycol derivatives of ethyleneoxide-propyleneoxide copolymer represented by the general formula:
R6xe2x80x94Oxe2x80x94Axe2x80x94R7xe2x80x83xe2x80x83(III)
and/or the general formula: 
wherein R6, R7, R8, R9 and R10 indicate each a hydrogen or an alkyl group having 1 to 3 carbon atoms, A is a polymerization chain of ethyleneoxide and propyleneoxide, consisting of p-times ethyleneoxide units and q-times propyleneoxide units, and p and q are numbers satisfying the requirements:
0.1xe2x89xa6p/q=10, 5xe2x89xa6p+qxe2x89xa6100.
Lubricating Oil IV
A lubricating oil for compression-type refrigerators, characterized by compounding a phosphate represented by the general formula: 
wherein R16 indicates a hydrogen or an alkyl group having 1 to 3 carbon atoms, r indicates an integer of 1 or 2, when r is 2, R16s may be identical or different and the total carbon number of (R16)r is not more than 3, with a base oil comprising, as the main component, polyoxyalkyleneglycol derivatives represented by the general formula:
R11xe2x80x94Oxe2x80x94A1xe2x80x94R12xe2x80x83xe2x80x83(VI)
and/or the general formula: 
wherein R11 to R15 indicate each a hydrogen or an alkyl group having 1 to 3 carbon atoms, and A1 to A3 indicate each polymerization chains consisting of 3 to 100 alkyleneoxide units of one kind or plural kinds, having 2 to 4 carbon atoms.
Lubricating Oil V
A lubricating oil for compression-type refrigerators, comprising, as the main component, polyoxyalkyleneglycol derivatives represented by the general formula: 
wherein R17, R18 and R19 indicate each an alkylene group having 2 to 4 carbon atoms, and s, t and u indicate each an integer of 1 to 30, and having a viscosity at 40xc2x0 C. of 50 to 250 cSt.
Lubricating Oil VI
A lubricating oil for compression-type refrigerator characterized by containing (a) polyoxyalkyleneglycol derivatives and (b) at least one compound selected from the group consisting of (i) dibasic acid ester, (ii) fluorinated oil, (iii) polyhydric alcohol ester, and (iv) silicone fluoride.
Lubricating Oil VII
A lubricating oil for refrigerator with compressor containing as the main component a polyoxyalkyleneglycol derivative represented by the general formula:
R40xe2x80x94Oxe2x80x94Axe2x80x94R41xe2x80x83xe2x80x83(XIV)
wherein R40 is an unsaturated hydrocarbon group having 2 to 10 carbon atoms (excluding aromatic hydrocarbon groups), A indicates a polymerization chain consisting of 3 to 90 alkyleneoxide units of one or plural kinds, having 2 to 4 carbon atoms, R41 is a hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or a cycloalkyl group having 4 to 20 carbon atoms. Additional Lubricating Oils including Lubricating Oil VIII and IX will be described hereinafter in greater detail.
First, Lubricating Oil I will be explained. Said Lubricating Oil I comprises as the main component a polyoxyalkyleneglycol derivative represented by the general formula (I) as described before.
In the formula, R1 is an alkyl group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, or an aliphatic hydrocarbon group having 2 to 6 valencies, R2 is an alkylene group having 2 to 4 carbon atoms, R3 is an alkyl group having 1 to 10 carbon atoms, or an acyl group having 1 to 10 carbon atoms, n is an integer of 1 to 6, and m is an integer of 1 to 80.
The alkyl group may be a straight chain alkyl group, branched chain alkyl group or cyclic alkyl group. Specific examples of these alkyl groups are a methyl group, an ethyl group, a n-propyl group, an isopropyl group, various butyl groups, various pentyl groups, various hexyl groups, various heptyl group, various octyl groups, various nonyl groups, various decyl groups, a cyclopentyl group, a cyclohexyl group and the like. If the carbon number of said alkyl group is in excess of 10, the compatibility with R-134a is reduced, which causes phase separation. The preferable carbon number of alkyl groups is 1 to 6. The most preferred lubricating oils of those represented by formula (I) are those wherein the R1 and R2 groups are alkyl groups, especially methyl groups.
The alkyl group in the acyl group may be a straight chain-, a branched chain-, or a cyclic alkyl group. Specific examples of the alkyl group in the acyl group are a methyl group, an ethyl group, an n-propyl group, an isopropyl group, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, a cyclopentyl group, a cyclohexyl group and the like.
If the carbon number of said acyl group is in excess of 10, the compatibility with R-134a is reduced, which causes phase separation. The preferable carbon number of the acyl group is 2 to 6.
When said R1 and R3 are each an alkyl group or an acyl group, R1 and R3 may be identical or different from each other.
Further, when n is 2 or more, plural R3 in one molecule may be identical or different.
In case R1 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms and 2 to 6 valencies, said aliphatic hydrocarbon group may be a chain or a cyclic group. Examples of aliphatic hydrocarbon groups having two valencies are an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a cyclopentylene group), and a cyclohexylene group. Examples of aliphatic hydrocarbon group having 3 to 6 valencies are residues resulting from removing a hydroxyl group from polyhydric alcohols such as trimethylol propane, glycerol, pentaerithritol, sorbitol, 1,2,3-trihydroxycyclohexane, and 1,3,5-trihydroxycyclohexane.
If the carbon number of said aliphatic hydrocarbon group is in excess of 10, the compatibility with R-134a is reduced, which causes phase separation. The preferable carbon number is 2 to 6.
In the before-mentioned general formula (I), R2 is an alkylene group having 2 to 4 carbon atoms, and as the oxyalkylene group of the repeating unit, an oxyethylene group, an oxypropylene group, and an oxybutylene group are specified. Oxyalkylene groups in one molecule may be identical or may vary in two or more kinds, but preferably at least an oxypropylene unit is contained in one molecule.
In the general formula (I), n is an integer of 1 to 6, and defined according to the number of valencies of R1. For example, when R1 is an alkyl group or an acyl group, n is 1. When R1 is an aliphatic hydrocarbon group having 2, 3, 4, 5 or 6 valencies, n comes to be 2, 3, 4, 5 or 6, respectively. m is an integer of 1 to 80, and if m is beyond the said range, the object of the present invention cannot attained sufficiently.
The general formula (I) means not only one kind of polyoxyalkyleneglycol derivatives but also a mixture of two or more kinds of the derivatives.
The polyoxyalkyleneglycol derivatives represented by the general formula (I) used in the said Lubricating Oil I can be produced according to various methods shown below.
Method (A)
Alkyleneoxide having 2 to 4 carbon atoms including ethyleneoxide and propyleneoxide are polymerized with water or alkali hydroxide as an initiator, to obtain a polyoxyalkyleneglycol having hydroxyl groups at the both terminals, represented by the general formula:
Hxe2x80x94(OR2)axe2x80x94OHxe2x80x83xe2x80x83(A1)
wherein a is a number of which mean value is 6 to 80, and R2 is as defined before. Subsequently, both the hydroxyl groups of said polyoxyalkyleneglycol are etherified or esterified or one of the hydroxyl groups is etherificated and the other hydroxyl group is esterified to obtain a polyoxyalkyleneglycol derivative represented by the general formula:
Rxe2x80x94(OR2)axe2x80x94ORxe2x80x2xe2x80x83xe2x80x83(A2)
wherein R and Rxe2x80x2 are each an alkyl group or an acyl group having 1 to 10 carbon atoms, and they may be identical or different each other, and R2 and a are as defined above.
Method (B)
Alkylene oxide having 2 to 4 carbon atoms is polymerized with monohydric alcohol having 1 to 10 carbon atoms or an alkali metal salt thereof as an initiator, to obtain a polyoxyalkyleneglycol monoalkylether represented by the general formula:
Rxe2x80x3xe2x80x94(OR2)axe2x80x94OHxe2x80x83xe2x80x83(B1)
wherein Rxe2x80x3 is an alkyl group having 1 to 10 carbon atoms, and R2 and a are as defined above, having an ether bond at one terminal and a hydroxyl group at the other terminal. Subsequently, the hydroxyl group of the polyoxyalkyleneglycol monoalkylether is etherified or esterified, to obtain a polyoxyalkyleneglycol derivative represented by the general formula:
Rxe2x80x3xe2x80x94(OR2)axe2x80x94ORxe2x80x83xe2x80x83(B2)
wherein R2 , R, Rxe2x80x3 and a are as defined above.)
Method (C)
Alkyleneoxide having 2 to 4 carbon atoms is polymerized with polyhydric alcohol having 2 to 6 valencies, and having 1 to 10 carbon atoms or alkali metal salt thereof as an initiator, to obtain a polyoxyalkyleneglycol derivative having a hydroxyl group at one terminal, represented by the general formula:
Rxe2x80x3xe2x80x2xe2x80x94[xe2x80x94(OR2)bxe2x80x94OH]cxe2x80x83xe2x80x83(C1)
wherein Rxe2x80x3xe2x80x2 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms and 2 to 6 valencies, c is an integer of 2 to 6, and b is a number, for which the mean value of bxc3x97c is 6 to 80, and R2 is as defined above. Subsequently, the hydroxyl group of the resulting polyoxyalkyleneglycol derivative is etherified or esterified, to obtain a polyoxyalkyleneglycol derivative represented by the general formula:
Rxe2x80x2xe2x80x3xe2x80x94[xe2x80x94(OR2)bxe2x80x94OR]cxe2x80x83xe2x80x83(C2)
wherein R2, R, Rxe2x80x3xe2x80x2, b and c are as defined above.
In these methods of production, in order to esterify the hydroxyl group of the polyoxyalkyleneglycol having a hydroxyl group at its terminal or derivatives thereof, usually performed are a method to react said substances with an aliphatic carboxylic acid having 1 to 10 carbon atoms or reactive derivatives such as acid anhydride, acid halide and ester thereof, or a method to convert the hydroxyl group of the said polyoxyalkyleneglycol or derivatives thereof to sulfonates or halides, which are reacted with said carboxylic acid or salt thereof.
Examples of said carboxylic acid are formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, capric acid, cyclohexanecarboxylic acid and the like.
When esterification is effected by the use of said carboxylic acid or acid anhydride thereof or by transesterification using the ester of said carboxylic acid, acid catalysts such as sulfuric acid and p-toluene sulfonic acid are usually used. When esterification is effected with the use of acid halides, usually amines are used as the dehydrohalogenating agent.
On the other hand in order to etherify the hydroxyl group of polyoxyalkyleneglycol having a hydroxyl group at its terminal or derivatives thereof, usually performed are a method to react them with alkali metals such as metallic sodium or alkali metal salts of lower alcohol such as sodium methoxide, to obtain alkali metal salt of said polyoxyalkyleneglycol or derivative thereof, and then react alkyl halide having 1 to 10 carbon atoms or sulfonates, or a method to transform the hydroxyl group of said polyoxyalkyleneglycol or a derivative thereof to sulfonate or halide, and then react them with aliphatic alcohol having 1 to 10 carbon atoms or alkali metal salts thereof.
In the polyoxyalkyleneglycol derivative thus obtained, the bonding style of the oxyalkylene unit is usually a head-tail bond in case of oxypropylene unit or oxybutylene unit, but head-head bonds and tail-tail bonds are also contained in some cases.
Lubricating Oil I of the present invention comprises, as the main component, the polyoxyalkyleneglycol derivative thus obtained and represented by the general formula (I), and said polyoxyalkyleneglycol derivative may be used solely or two or more kinds of them may be used in combination. Said lubricating oil can be favorably used even if it contains, in addition to the before-mentioned polyoxyalkyleneglycol derivative represented by the aforementioned general formula (I), a polyoxyalkyleneglycol derivative having hydroxyl group(s) at its terminals as long as the content of said hydroxyl groups is not more than 30 mol % of the total terminal groups.
The object of the present invention cannot be attained with polyoxyalkyleneglycol derivative wherein R1 and R3 are aromatic groups in the before-mentioned general formula (I), though the reason for this is not clear.
Preferred are the polyoxyalkyleneglycol derivatives of the general formula (I) wherein n is 1, and R1 and R3 are methyl groups.
The reasons for this preference is that (1) polyoxyalkylene derivatives having a hydroxy group at the terminal of the molecule (one terminal or both terminals) might cause the blocking of the expansion bulbs by icing since the derivatives dissolve a relatively large amount of water therein. (2) Accordingly, compounds having alkyl groups at both terminals are preferred since they are free from blocking of expansion bulbs as heretofore described, among all compounds, those having methyl groups at both terminals are most preferred. The derivatives have a highly favorable compatibility with the refrigerant R-134a.
Lubricating Oil I of the present invention is preferred to have a viscosity at 100xc2x0 C. in the range of 2 to 50 cSt, more preferably 5 to 30 cSt, much more preferably 6 cSt (n=1, m=12 in the general formula (I)) to 30 cSt, still more preferably 7 cSt (n=1, m=14) to 30 cSt, and most preferably 9 cSt (n=1, m=19) to 30 cSt in order to retain the thickness of oil film necessary for lubricating and to maintain sufficient sealing properties. If necessary, to lubricating Oil I of the present invention can be added, various additives used in conventional lubricating oils such as anti-load additives, chlorine capturing agents, antioxidants, metal deactivating agents, defoaming agents, detergent dispersants, viscosity index improvers, oilness agents; antiwear additives, extreme pressure agents, rust inhibitors, anti-corrosion agents, pour point depressants and the like.
The above-mentioned anti-load additives include organic sulfide-based additives such as monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized fats and oils, thiocarbonates, thiophenes, thiazols, methanesulfonic acid esters; phosphate-based additives such as phosphoric monoesters, phosphoric diesters and phosphoric triesters (tricresyl phosphate); phosphite-based additives such as phosphorous monoesters, phosphorous diesters, and phosphorous triesters; thiophosphate-based additives such as thiophosphoric acid triesters; fatty acid-based additives such as higher fatty acid, hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters, and metal soap; fatty acid ester-based additives such as polyhydric alcohol esters and acrylic acid esters; organic chlorine-based additives such as chlorinated hydrocarbons and chlorinated carboxylic acid derivatives; organic fluorine-based additives such as fluorinated aliphatic acids, ethylene fluoride resins, fluoroalkyl polysiloxanes and fluorinated graphite; alcohol-based additives such as higher alcohols; and metallic compound-based additives such as naphthenates (lead naphthenate), fatty acid salts (fatty acid lead), thiophosphates (zinc dialkyldithiophosphate), thiocarbamates, organomolybdenum compounds, organic tin compounds, organo-germanium compounds, and boric acid esters.
Chlorine capturing agents include compounds having glycidyl ether group, epoxyfatty acid monoesters, epoxy fats and oils and compounds having an epoxycycloalkyl group. Antioxidants include phenols (2,6-di-tert-butyl-cresol), aromatic amines (alpha-naphthylamine) and the like. Metal deactivators include benzotriazole derivatives. Defoaming agents include silicone oil (dimethylpolysiloxane), and polymethacrylates. Detergent dispersants include sulfonates, phenates, succinimides and the like.
Viscosity index improvers include polymethacrylate, polyisobutylene, ethylene-propylene copolymer, hydrogenated styrene-diene copolymer and the like.
Lubricating Oil I of the present invention having a high compatibility with refrigerants as well as excellent lubricating ability is used for compression-type refrigerators, and it is particularly suitable for compression-type refrigerators employing R-134a as the refrigerant, since said lubricating oil has a good compatibility with R-134a, unlike the conventional lubricating oils. Moreover, Lubricating Oil I can be used in mixture with another lubricating oil for compression-type refrigerators, with the purpose of improving its compatibility with refrigerants.
The description of the aforesaid Lubricating Oil II is as follows. This Lubricating Oil II contains a polyoxyalkyleneglycol derivative represented by the general formula (II) as aforementioned as a main component. Here in the formula, R4 is an alkyl group having 1 to 3 carbon atoms, R5 is an alkylene group having 2 to 4 carbon atoms and k is a number of 6 to 80, preferably 10 to 40.
The alkyl group of this lubricating oil is any of a methyl group, an ethyl group, a propyl group or an isopropyl group. If this alkyl group has 4 or more carbon atoms, compatibility with a hydrogen-containing fluorocarbon compound such as R-134a, etc. is reduced and phase separation comes to occur. Of these alkyl groups, a methyl group is particularly preferred.
R5 in the aforesaid general formula (II) is an alkylene group having 2 to 4 carbon atoms as heretofore described. Consequently, oxyalkylene groups having a repeating unit represented by OR5 include an oxyethylene group, an oxypropylene group and an oxybutylene group. Oxyalkylene groups in one molecule may be the same or two or more kinds of oxyalkylene groups may be contained in one molecule. However, it is preferred to contain at least one oxypropylene unit in one molecule. An alkylene group in an oxyalkylene group may be a straight-chain group or branched group.
The k in the general formula (II) is a number of 6 to 80 on the average, preferably 10 to 40. If this average value is too small, lubrication is reduced, and if it is too large, solubility decreases, so the objects of the present invention cannot be satisfactorily attained.
The polyoxyalkyleneglycol derivative, which is represented by the aforesaid general formula (II), to be used as the lubricating oil of the present invention, can be produced, for example, by the following methods.
Method (D)
Polyoxyalkyleneglycol having hydroxyl groups at both terminals represented by the general formula:
H(OR5)kOHxe2x80x83xe2x80x83(D1)
wherein R5 and k are the same as the foregoing is obtained by polymerizing alkylene oxide having 2 to 4 carbon atoms such as ethylene oxide and propylene oxide, and water or alkali hydroxide as an initiator and then a polyoxyalkyleneglycol derivative represented by the general formula:
R4(OR5)kOHxe2x80x83xe2x80x83(II)
wherein R4, R5 and k are the same as the foregoing is obtained by etherifying one of the hydroxyl groups.
The etherification can be carried out by various methods, for example, the reaction of polyoxyalkyleneglycol with dialkyl sulfate, the reaction of alkoxide in polyoxyalkylene glycol with alkyl halide or the reaction of halogenated polyoxyalkyleneglycol wherein one terminal hydroxy group is halogenated, with alkoxide, and the others.
The reaction of polyoxyalkyleneglycol with dialkyl sulfate is usually carried out in the presence of an aqueous alkali solution at a temperature of xe2x88x9210xc2x0 C. to 100xc2x0 C. for 5 minutes to 50 hours. When the reaction is carried out at a temperature of more than 40xc2x0 C., one of two alkyl groups contained in alkyl sulfate reacts, and at a temperature of more than 50xc2x0 C., both alkyl groups react. If necessary, an inert liquid can be used as a solvent. Dialkyl sulfates include dimethyl sulfate, diethyl sulfate, dipropyl sulfate and diisopropyl sulfate. Aqueous alkalis include sodium hydroxide, potassium hydroxide and the like.
The reaction of alkoxide in polyoxyalkyleneglycol with halogenated alkyl is usually carried out at atmospheric pressure or under pressure at a temperature of 50xc2x0 C. to 150xc2x0 C. for 30 minutes to 30 hours. Solvents such as toluene, tetrahydrofuran and the like can be used preferably. Halogenated alkyls include methyl chloride, methyl bromide, methyl iodide, ethyl chloride, propyl chloride, isopropyl chloride and the like.
The method in which one terminal hydroxyl group of polyoxyalkyleneglycol is reacted with alkoxide after halogenating is that derivative in which hydroxy group at the terminal is halogenated, obtained by reacting polyoxyalkylene glycol with halogenating reagents such as thionyl chloride, phosphorus pentachloride, phosphorus pentabromide and the like is reacted with alkoxide at a temperature of 50xc2x0 C. to 150xc2x0 C. for 30 minutes to 30 hours. Alkoxides include sodium methoxide, potassium methoxide, sodium ethoxide, sodium propoxide, sodium isopropoxide and the like.
In the above Method (D), besides a polyoxyalkyleneglycol derivative wherein one terminal of polyoxyalkyleneglycol is alkylether and the other terminal thereof is a hydroxyl group, a polyoxyalkyleneglycol derivative and a polyoxyalkylene glycol material both terminals of which are alkylethers are included. Polyoxyalkyleneglycol with alkylether at one of the terminals can be separated to be used. Also, it can be used as a mixture without separating these components.
Method (E)
A polyoxyalkyleneglycol derivative represented by the general formula:
R4(OR5)kOHxe2x80x83xe2x80x83(II)
wherein R4, R5 and k are the same as the foregoing is obtained by polymerizing alkylene oxide having 2 to 4 carbon atoms and monohydric alcohol having 1 to 3 carbon atoms or its alkali metal salt as an initiator.
When alcohol is used as a material, aqueous alkali of 0.05 to 1.3 equivalent to alcohol is used. Alcohol, and aqueous alkali or alkali metal salt of alcohol are introduced in an autoclave and heated to a temperature of 50xc2x0 C. to 150xc2x0 C. The prescribed amount of alkylene oxide is introduced therein under pressure for 10 minutes to 50 hours while stirring to obtain the desired polyoxyalkyleneglycol derivative. Monohydric alcohols include methanol, ethanol, propanol and isopropanol. Alkali metal salts of monohydric alcohol include sodium methoxide, potassium methoxide, sodium ethoxide, sodium isopropoxide and the like.
In the above Method (E), only a polyoxyalkyleneglycol derivative with alkylether at one terminal of the polyoxyalkyleneglycol and a hydroxyl group at the other terminal thereof, is obtained. Therefore, Method (E) is preferable to Method (D) as the case may be.
A polyoxyalkyleneglycol derivative thus obtained may be used alone or in a mixture comprising two or more thereof.
The viscosity of Lubricating Oil II at 100xc2x0 C. is preferably in the range of 2 to 50 cSt in order to maintain a thickness of oil film sufficient to lubricate.
To Lubricating Oil II of the present invention, in the same way as in the above Lubricating Oil I, various additives used in conventional lubricating oils can be added, if desired, for example, an anti-load additive, a chlorine capturing agent, an antioxidant, a metal deactivator, a defoaming agent, a detergent dispersant, a viscosity index improver, an oiliness agent, an anti-wear additive, an extreme pressure agent, a rust preventative, a corrosion inhibitor, a pour point depressant and the like. Specific examples thereof are the same as described before.
Subsequently, the detailed description of Lubricating Oil III in the present invention is as follows.
Lubricating Oil III contains a polyoxyalkyleneglycol derivative comprising an ethylene oxide-propylene oxide copolymer represented by the aforesaid general formula (III) and/or (IV) as a main component. R6, R7, R8, R9 and R10 indicate each a hydrogen or an alkyl group having 1 to 3 carbon atoms (a methyl group, an ethyl group, an n-propyl group, an i-propyl group). Particularly, both R6 and R7, or R8, R9, and R10 are preferably all alkyl groups, preferably methyl groups. A is a copolymer chain of p-times of ethylene oxide unit and q-times of propylene oxide unit and the form of the copolymer may be any of block copolymers, random copolymers, alternating copolymers and so on. p and q satisfy the following requirements: 0.1xe2x89xa6p/qxe2x89xa610, preferably 0.1xe2x89xa6p/qxe2x89xa63, most preferably 0.2xe2x89xa6p/qxe2x89xa62, and also 5xe2x89xa6p+qxe2x89xa6100, preferably 5xe2x89xa6p+qxe2x89xa650. In this way, a polyoxyalkyleneglycol derivative of the general formula (III) and/or (IV) to be used in Lubricating Oil III of the present invention must contain an ethylene oxide unit and a propylene oxide unit in the specified proportion. If p/q is less than 0.1, there may occur the problems that a viscosity index decreases and solubility also is reduced. If it exceeds 10, there are troubles that the product becomes a wax state and solubility lowers. Further, if p+q is less than 5, there is a problem that lubricity decreases because the viscosity is too small. If it exceeds 100, solubility and heat exchange efficiency decrease undesirably.
Hereinafter, an ethylene oxide unit is referred to as EO, a propylene oxide unit is referred to as PO and A is referred to as xe2x80x94(EO)mxe2x80x94(PO)nxe2x80x94 to make understanding of the invention simple. These are not limited in a block copolymer but widely applied to a random copolymer, an alternating copolymer and the like.
Specific examples of a polyoxyalkyleneglycol derivative of the general formula (III) or (IV) to be used in the present invention are:
xe2x80x83H3Cxe2x80x94Oxe2x80x94(EO)20xe2x80x94(PO)20xe2x80x94CH3,
Hxe2x80x94Oxe2x80x94(EO)4xe2x80x94(PO)14xe2x80x94CH3,
Hxe2x80x94Oxe2x80x94(EO)15xe2x80x94(PO)15xe2x80x94H,

The above repeating unit numbers of EO and PO are shown only as examples, and they can not be limited so far as the aforesaid conditions are satisfied.
In Lubricating Oil III of the present invention, a polyoxyalkyleneglycol derivative of the above general formula (III) or (IV) may be used alone or in a mixture comprising two or more thereof.
Lubricating Oil III of the present invention contains the above polyoxyalkyleneglycol derivative as a main component. In the same way as in the aforesaid Lubricating Oil I, various additives used in conventional lubricating oils, for example, an anti-load additive, a chlorine capturing agent, an antioxidant, a metal deactivator, a defoaming agent, a detergent dispersant, a viscosity index improver, an oiliness agent, an anti-wear agent, an extreme pressure agent, a rust preventative, a corrosion inhibitor, a pour point depressant and the like, and further, a mineral oil and a synthetic oil used as a base oil for a lubricating oil, can be added thereto, if desired. Specific examples thereof are the same as aforementioned.
Further, the description of Lubricating Oil IV in the present invention is as follows.
Lubricating Oil IV of the present invention contains a polyoxyalkyleneglycol derivative represented by the aforesaid general formula (V) and/or (VI) as a main component. R11, R12, R13, R14 and R15 indicate each a hydrogen or an alkyl group having 1 to 3 carbon atoms (a methyl group, an ethyl group, an n-propyl group, an iso-propyl group). Particularly, R11 to R15 are preferably all alkyl groups, most preferably methyl groups. A1 to A3 are (co)polymer chains comprising 3 to 100 preferably 3 to 50 of one, two or more kinds of alkylene oxide units having 2 to 4 carbon atoms. The numbers 3 to 100 representing the above unit number indicate the mean value of polymerization numbers of an alkylene oxide unit (an ethylene oxide-unit, a propylene oxide unit, a butylene oxide unit) and real numbers containing integers. That is, they are block copolymer chains, random copolymer chains or alternating copolymer chains containing d-times alkylene oxide units represented by the general formula:
xe2x80x94(RdO)xe2x80x94
wherein Rd is an alkylene group having 2 to 4 carbon atoms and e-times of alkylene oxide unit represented by the general formula:
xe2x80x94(ReO)xe2x80x94
wherein Re is an alkylene group having 2 to 4 carbon atoms, and d and e are each 0 to 100 satisfying the requirement d+e=3 to 100. When either d or e is 0, they become homopolymer chains of the other alkylene oxide unit.
If d+e exceeds 100, compatibility decreases to separate undesirably.
Specific examples of a polyoxyalkyleneglycol derivative represented by the general formula (V) or (VI) to be used in the present invention are:
HO(C3H6O)4xcx9c40H
H3CO(C3H6O)4xcx9c40CH3
HO(C3H6O)2 30xe2x80x94(C2H4O)2xcx9c30CH3
H3CO(C3H6O)2xcx9c30xe2x80x94(C2H4O)2xcx9c30CH3

Copolymers referred to as the above block copolymerization contains not only block copolymers but also random copolymers or alternating copolymers.
In Lubrication Oil IV of the present invention, a polyoxyalkyleneglycol derivative of the above formula (VI) or (VII) may be used alone or in a mixture comprising two or more of both types.
In the present invention, phosphate represented by the aforesaid formula (V) is blended with a base oil containing a polyoxyalkyleneglycol derivative as a main component as described above. R16 as well as the aforesaid R11 to R15 indicates hydrogen or an alkyl group having 1 to 3 carbon atoms and r indicates an integer of 1 or 2. If two R16s are present, they may indicate different alkyl groups, but the total of carbon atoms in them must be 3 or less.
Specific examples of such phosphate represented by the general formula (V) are tricresol phosphate (TCP), triphenyl phosphate, tri-isopropylphenyl phosphate and so on. Of these, it is preferable to use tricresol phosphate.
In the present invention, the amount of the above phosphate to be blended is usually determined appropriately within the range of 0.1 to 5% by weight, preferably 0.2 to 3% by weight based on the total amount of a refrigerating machine oil to be prepared.
In Lubricating Oil IV of the present invention, by combining a polyoxyalkyleneglycol derivative having the aforesaid structure and the above phosphate, the effect of the phosphate as an anti-wear agent shows sufficiently and also the anti-seizure property improves, bad influences such as deterioration of appearance and lowering of high critical dissolution temperature decrease and, ""lubricity as a refrigerating machine oil improves.
Lubricating Oil IV of the present invention usually contains the above polyoxyalkyleneglycol derivative as a main component, whereto phosphate of the general formula (V) is blended. In addition, various additives used in conventional lubricating oils, for example, an anti-load additive, a chlorine capturing agent, an antioxidant, a metal deactivator, a defoaming agent, a detergent dispersant, a viscosity index improver, an oiliness agent, an anti-wear additive, an extreme pressure agent, a rust preventative, a corrosion inhibitor, a pour point depressant and the like can be blended.
And further, as a base oil besides the above polyoxyalkyleneglycol derivative, a mineral oil and a synthetic oil used as a base oil for a lubricating oil can be added thereto, if desired. Specific examples thereof are the same as described before.
Further, the description of Lubricating oil V in the present invention is as follows.
This Lubricating Oil V is a compound obtained by adding alkylene oxide to glycerol, as shown in the general formula (VIII), wherein R17, R18 and R19 may be the same alkylene groups or different alkylene groups.
Alkylene oxide added in the polyoxyalkyleneglycol derivative to be used in the present invention, having 2 to 6 carbon atoms, such as ethylene oxide, propylene oxide, butylene oxide and the like can be used.
In the formula, additional numbers s, t and u are integers of 1 to 30, preferably 2 to 15.
The polyoxyalkyleneglycol derivative of the general formula (VIII) can be used as a mixture having the different additional number of moles.
The viscosity of the polyoxyalkyleneglycol derivative depends on the type of an alkylene group and the additional number of moles (s, t, u).
A polyglycol compound to be used in the present invention needs to have a viscosity of 50 to 250 cSt, preferably 60 to 200 cSt at 40xc2x0 C. If the viscosity is less than 50 cSt, the sealing property becomes inferior, and if it exceeds 250 cSt, the polyoxyalkyleneglycol derivative becomes insoluble in a refrigerant.
According to the desired viscosity, the type and the average additional number of moles can be determined.
Such polyoxyalkyleneglycol derivative obtained by adding propylene oxide or ethylene oxide to glycerol can be preferably used.
For example, a propylene oxide adduct of glycerol represented by the formula: 
has a viscosity of 116 cSt at 40xc2x0 C. A propylene oxide adduct of glycerol represented by the formula: 
has a viscosity of 103 cSt at 40xc2x0 C. Both can be preferably used.
It is preferred that the purity of the polyoxyalkyleneglycol derivative to be used in the present invention is 70% or more by weight.
In Lubricating Oil V of the present invention, a mineral oil or a synthetic oil can be blended to the above polyglycol compound to the amount of 50% or less by weight.
A mineral oil or a synthetic oil having a viscosity of 5 to 500 cSt at 40xc2x0 C. can be preferably blended. For example, (i) a paraffinic mineral oil, (ii) a naphthenic mineral oil, (iii) poly (Y-olefin, (iv) alkylbenzene, (v) alkyldiphenyl, (vi) ester (hindered ester, dibasic acid ester, polyolester, phosphate), (vii) polyglycol (polyphenyleneglycol, monofunctional- and difunctional-polyglycol) and the like can be used. Of these, synthetic oils (iv) to (vii) having high solubility in a refrigerant can be most preferably blended. If the viscosity of these mixed oils becomes less than 5 cSt, the amount of oil by circulation increases, losses due to evaporation become large and a disadvantage of poor sealing property occurs.
In Lubricating Oil V, it is preferred to maintain the water content at 500 ppm or less, preferably 300 ppm or less, more preferably 200 ppm or less and most preferably 100 ppm or less.
If the water content increases, rust is liable to form and further, solubility decreases. Though Lubricating Oil V is excellent in various properties as described above, it is relatively inferior in wear resistance to other Lubricating Oils, Lubricating Oils I to IV and VI.
In Lubricating Oil V of the present invention, additives to be added usually, for example, an anti-wear agent, an antioxidant, a metal deactivator, a chlorine capturing agent a defoaming agent and the others can be added appropriately, if desired.
Next, Lubricating Oil VI of the present invention will be explained. In said Lubricating Oil VI, polyoxyalkyleneglycol derivative used as component (a) is not critical, but it is preferred to use at least one compound selected from a compound represented by the general formula:
R20xe2x80x94Oxe2x80x94(R21O)wR22xe2x80x83xe2x80x83(IX)
wherein R20 and R22 are each a hydrogen, a hydrocarbon group or an acyl group, and may be identical or different from each other, R21 is an alkylene group having 2 to 6 carbon atoms, and w is a number of 2 or more and a compound represented by the general formula: 
wherein R23, R24 and R25 are each an alkylene group having 2 to 6 carbon atoms, which may be identical or different from each other, R26, R27 and R28 are each a hydrogen atom, a hydrocarbon group or an acyl group, which may be identical or different from each other, and x, y and z are each a number of 2 or more, which may be identical or different from each other.
R20 and R22 in the general formula (IX), R26, R27 and R28 in the general formula (X) are each a hydrogen atom, a hydrocarbon group or an acyl group, and said hydrocarbon groups include an alkyl group, a cycloalkyl group or an aryl group each having 1 to 30, preferably 1 to 12 carbon atoms. Examples of such hydrocarbon groups are a methyl group, an ethyl group, an n-propyl group, an isopropyl group, various butyl groups, various pentyl groups, various hexyl group, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various undecyl groups, various dodecyl groups, various cyclopentyl groups, a cyclohexyl group, a methylcyclohexyl group, a phenyl group, a tolyl group, a benzyl group, a phenethyl group and the like.
Acyl groups includes those groups derived from aliphatic carboxylic acids, alicyclic compounds, or aromatic carboxylic acids each having 1 to 30, preferably 1 to 12 carbon atoms. Examples of such acyl groups are those derived from carboxylic acids including formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, cyclohexane carboxylic acid, and benzoic acid.
R21 in the general formula (IX), R23, R24 and R25 in the general formula (X) are each an alkylene group having 2 to 6 carbon atoms, preferably an ethylene group, a propylene group, or a butylene group. In polyoxyalkyleneglycol derivative represented by the general formulas (IX) and (X), the oxyalkylene group as the repeating unit contained in one molecule may be identical or different.
R20 and R22 in the general formula (IX) may be identical or different from each other, but preferably either of them is a hydrocarbon group, more preferably an alkyl group. Specific examples of the polyglycol compounds represented by said general formula (IX) are,
C9H19O(C3H6O)10H
C4H9O(C3H6O)18H
HO(C3H6O)17H
R23, R24 and R25 in the general formula (X) may be identical or different from each other. R26, R27 and R28 may be identical or different from each other, but preferably all of them are hydrogen atoms. Furthermore, x, y and z may be identical or different from one another. A specific example of such a compound is: 
Polyoxyalkyleneglycol derivative represented by the general formula (IX) or (X) can be produced according to a conventional process. For example, in a process for producing the polyoxyalkyleneglycol derivative represented by the general formula (IX), an alkyleneoxide having 2 to 6 carbon atoms such as ethyleneoxide or propyleneoxide is polymerized with water or alkali hydroxide as an initiator, to obtain a polyglycol having hydroxyl groups at both terminals, and if one of or both the hydroxyl groups of the polyglycol thus obtained is/are etherified or esterified according to conventional processes, polyoxyalkyleneglycol derivatives having ether bond or ester bond at terminals can be obtained.
Further, if alkyleneoxide having 2 to 6 carbon atoms is polymerized with the use of alcohols having the desired carbon number or phenols or alkali metal salts thereof as an initiator, polyoxyalkyleneglycol derivatives having an ether bond at one terminal and a hydroxyl group at the other terminal can be obtained. And if the hydroxyl groups of said derivative are etherified or esterified, a polyoxyalkyleneglycol derivative having ether bonds or ether bond and ester bond at both the terminals can be obtained.
In a process for producing polyoxyalkyleneglycol derivatives represented by the general formula (X), if an alkyleneoxide having 2 to 6 carbon atoms is polymerized with the use of glycerol or alkali metal salts thereof as an initiator, a polyglycolether of glycerol having three hydroxyl groups at the terminals can be obtained, and if the hydroxyl groups of the said polyglycolether are etherified or esterified according to a conventional process, a polyglycol ether (polyoxyalkyleneglycol derivative) of glycerol having ether bonds or ester bonds at the terminals can be obtained.
In Lubricating Oil VI in the present invention, one of the above-mentioned component (a) may be used solely, or two or more kinds may be used in combination.
In Lubricating Oil VI of the present invention, at least one compound selected from the group consisting of (i) dibasic acid ester, (ii) fluorinated oil (iii) polyhydric alcohol ester, and (iv) fluorosilicone is used as component (b).
As the dibasic acid ester of component (i), for example, a compound represented by the general formula:
R29OOCxe2x80x94A4xe2x80x94COOR30xe2x80x83xe2x80x83(XI)
wherein R29 and R30 are each an alkyl group, a cycloalkyl group or an aryl group each having 1 to 20 carbon atoms and may be identical or different from each other, and A4 is an alkylene group, a cycloalkylene group or a phenylene group, is used. Typical examples of such dibasic acid esters are di-2-ethylhexyl adipate, di-2-ethylhexyl sebacate, cyclohexane-1,4-dicarboxylic acid di-2-ethylhexyl, diisodecyl phthalate and the like.
A preferred example of the fluorinated oil as component (ii) is monochlorotrifluoroethylene polymer represented by the general formula: 
wherein X and X are each a halogen atom, and may be identical or different from each other, and j is a number, for which average molecular weight is 250 to 1500. As the said monochlorotrifluoroethylene polymer, Daifloil 10 and Daifloil 20 (Trade Mark, both produced by Daikin Industry Co., Ltd.) are commercially distributed.
Preferable examples of polyalcoholester as component (iii) are monovalent or divalent aliphatic esters of polyhydric alcohols such as neopentyl glycol, glycerol, trimethylol ethane, trimethylol propane, pentaerithritol, and sorbitol.
Typical examples of such polyhydric alcohol esters are trimethylol propane caproic acid ester, pentaerithritol propionic acid ester, pentaerithritol caproic acid ester, trimethylol prouane adipic acid ester and the like.
An Example of fluorosilicone as component (iv) is a compound represented by the general formula: 
wherein at least one of R31, R32, R33, R34, R35 and R36 is a fluorohydrocarbon group having 1 to 30 carbon atoms, and others are hydrocarbon groups, acyl groups, alkoxyl groups or fluorohydrocarbon groups each having 1 to 30 carbon atoms, and may be identical of different from one another, and v is 0 or an integer of 1 or more.
The hydrocarbon group in the fluorosilicone represented by the general formula (XIII) is an alkyl group, a cycloalkyl group or an aryl group, and in the fluorohydrocarbon group, at least one hydrogen atom of these hydrocarbon groups is substituted by a fluorine atom.
Further, in said alkoxyl group and acyl group, when oxygen atom or carbonyl group is removed, the residues comprise an alkyl group, a cycloalkyl group or an aryl group. Typical example of such a fluorosilicone is LS-8210 (Trade Mark, produced by Shin-etsu Chemical Industry Co., Ltd.), which is commercially available.
In Lubricating Oil VI of the present invention, at least one compound selected from the group consisting of component (i), component (ii), component (iii) and component (iv) is compounded as component (b) with component (a). The amount of said component (b) is defined usually in the range of 0.01 to 50% by weight, particularly in the range of 0.1 to 30% by weight of the total amount of component (a) and component (b). If the amount is less than 0.01% by weight, the effect of improving solubility at high temperatures to fluoroalkanes as refrigerant is not shown sufficiently, and if it is in excess of 50% by weight, stability or blend stability will be reduced.
Lubricating Oil VI of the present invention can be added with various additives which are conventionally used for refrigerator oils, as long as the object of the present invention might not be hindered. Examples of such additives are anti-wear agents, antioxidants, metal deactivators, chlorine capturing agents, defoaming-agents, pour point depressants, viscosity index improvers and the like.
The lubricating oils of the present invention are excellent in compatibility with refrigerants and in lubricating property, and accordingly utilized as lubricating oils for various refrigerating machines using fluoroalkane (flon) refrigerant, including a compression-type refrigerators. Particularly, unlike the conventional lubricating oils, the lubricating oil in the present invention has good compatibility with hydrogen-containing fluorocarbon compounds (hydrogen-containing fluoroalkane) such as R-134a and the like, for example, 1,1,2,2tetrafluoroethane (R-134), 1,1-dichloro-2,2,2trifluoroethane (R-123), 1-chloro-1,1-difluoroethane (R-142b), 1,1-difluoroethane (R-152a), chlorodifluoromethane (R-22), trifluoromethane (R-23). This solubility is satisfactory throughout the whole temperature range.
Consequently, the lubricating oil in the present invention can be expected to be effectively used as a lubricating oil for refrigerators using various hydrogen-containing fluorocarbon compounds as a refrigerant, a cooler (particularly car air-conditioner), a heat pump and the like. Also, this lubricating oil can be used by mixing with other lubricating oils for compression-type refrigerators.
An explanation of the Lubricant Oil VII which polyoxyalkyleneglycol derivative represented by the general formula (XIV) is as follows:
Herein R40 is an unsaturated hydrocarbon group having 2 to 10 carbon atoms excluding aromatic unsaturated hydrocarbons, such as an alkenyl group, an alkynyl group, a cycloakenyl group, more specifically a vinyl group, an allyl group, an isopropenyl group, a butenyl group, ethynyl group, propynyl group and butynyl group.
R41 is as described before, a hydrogen, an alkyl group having 1 to 20 carbon atoms (including a methyl group, an ethyl group, a propyl group, and butyl group), an alkenyl group having 2 to 20 carbon atoms (including a vinyl group, an allyl group, and a butenyl group), an alkynyl group having 2 to 20 carbon atoms (including an ethynyl group, and propynyl group), an aryl group having 6 to 20 carbon atoms (including a phenyl group, a tolyl group, a xylyl group, a nonylphenyl group, and a dodecylphenyl group, an aralkyl group having 7 to 20 carbon atoms (including a benzyl group and a phenethyl group) or a cycloalkyl group having 4 to 20 carbon atoms (including a cyclohexyl group, a cycloheptyl group, a methylcyclohexyl group, and a nonylcyclohexyl group). Among them, preferred are a hydrogen, an alkyl group having 1 to 4 carbon atoms and an alkenyl group having 2 to 4 carbon atoms.
A is a (co)polymerization chain consisting of 3 to 90-times, preferably 3 to 50-times alkyleneoxide units of one or plural kinds, having 2 to 4 carbon atoms. Therein, the numbers 3 to 90 representing the above unit number indicates the mean value of the polymerization degree of alkyleneoxide unit (an ethyleneoxide unit, a propyleneoxide unit, a butyleneoxide unit), showing real numbers including integers.
That is, A is a block copolymerization chain, a random copolymerization chain, or an alternating copolymerization chain containing a-times alkyleneoxide units represented by the general formula:
xe2x80x94(R42O)xe2x80x94
wherein R42 indicates an alkylene group having 2 to 4 carbon atoms and b-times alkyleneoxide units represented by the general formula:
xe2x80x94(R42xe2x80x2xe2x80x94O)xe2x80x94
wherein R42xe2x80x2 is an alkylene group having 2 to 4 carbon atoms, and a and b are each a number of 0 to 90, satisfying the requirement: a+b=3 to 90. In case either of a and b is 0, the polymer chain becomes a homopolymerization of another alkyleneoxide unit.
Herein, if a+b exceeds 90, compatibility with a refrigerant decreases to cause two-layer separation undesirably.
Examples of polyoxyalkyleneglycol derivatives represented by the general formula (XIV) mentioned above are:
CH2xe2x95x90CHxe2x80x94CH2O(C3H6O)4xcx9c40H
CH2xe2x95x90CHxe2x80x94CH2O(C3H6O)4xcx9c40CH3
CH2xe2x95x90CHxe2x80x94CH2O(C3H6O)4xcx9c40xe2x80x94CH2CHxe2x95x90CH2
CH2xe2x95x90CHxe2x80x94CH2O(C3H6O)2xcx9c20xe2x80x94(C2H4O)2 20xe2x80x94CH3
CH2CHO(C3H6O)4xcx9c40H
CH2xe2x95x90CHO(C3H6O)4xcx9c40CHxe2x95x90CH2
CH2xe2x95x90CHO(C3H6O)4xcx9c40CH3
CHxe2x95x90CO(X3H6O)4xcx9c40H
CHxe2x95x90CO(C3H6O)4xcx9c40Cxe2x89xa1CH
(copolymers shown by the above block copolymerization includes not only block copolymers but also random copolymers or alternating copolymers.)
Lubricating oil VIII of the invention comprises components (A) and (B) as the main components, wherein component (A) is polyoxypropyleneglycol dimethylether having a kinematic viscosity of 2 to 50 cSt, preferably 5 to 30 cSt at 100xc2x0 C., and specifically represented by the formula:
CH3O(C3H6O)mCH3xe2x80x83xe2x80x83XV
wherein m indicates the degree of polymerization and component (B) is a compound represented by the general formula:
CH3O(C2H4O)x(RO)yCH3
wherein R indicates a propylene group or butylene group, x and y indicate real numbers satisfying the requirements:
0.01 less than 44x/M
in which M is the molecular weight of the compound represented by the above formula and
5xe2x89xa6x+yxe2x89xa6100;
however, when x is a plural number, Rs may be identical to or different from each other, in such a ratio that the content of ethylene oxide unit (C2H4O) may be 1 to 30% by weight based on the total weight of (A) and (B).
In the above formula XV, both the terminals must be methyl groups. If either or both of the terminals are ethyl groups and the like, said lubricating oil becomes poor in compatibility with R-134a. However, polyoxypropyleneglycol monomethylether, polypropyleneglycol and the like can be contained, provided that it is in a small amount of 30% by weight or less based on the total amount of component (A).
Component (B) of Lubricating Oil VIII of the invention is, as described above, a compound represented by the general formula XVI:
CH3O(C2H4O)x(RO)yCH3xe2x80x83xe2x80x83XVI.
Representative compounds are polyoxyethylene polyoxypropyleneglycol dimethylether, polyoxyethylene polyoxybutyleneglycol dimethylether, or polyoxyethylene polyoxypropylene polyoxybutyleneglycol dimethylether or mixtures thereof. In the general formula XVI, R indicates an oxypropylene group (or propylene oxide group) (C3H6O) or an oxybutylene group (or butylene oxide group) (C4H8O), or a mixture thereof; x and y are real numbers satisfying 0.01 less than 44x/M (M is the molecular weight of the compound represented by the above formula XVI), and 5xe2x89xa6x+yxe2x89xa6100. More specifically, x and y satisfy the requirements: 1xe2x89xa6xxe2x89xa6100, 0xe2x89xa6yxe2x89xa699 and 0.1xe2x89xa6x/(x+y)xe2x89xa61. The most preferred x and y are those which satisfy the requirements: 10xe2x89xa6x+yxe2x89xa650 and 0.2xe2x89xa6x/(x+y)xe2x89xa61.
Satisfying the equation 0.01 less than 44x/M means that the content of ethyleneoxide unit (C2H4O) exceeds 0.01 (ratio by weight) of the compound represented by the general formula XVI. If the value of 44x/M is 0.01 or less, the content of the ethylene oxide unit in the mixture does not reach the prescribed value, to lead to an insufficient antiwear property.
Also in component (B), both the terminals of the molecule should be methyl groups (that means dimethylether) like component (A). If either one or both of the terminals are ethyl groups, propyl groups and the like, the compatibility with R-134a becomes low. In the general formula XVI, a block polymer is shown for convenience, but actually it is not limited to block polymer, but may be random polymer, alternating polymer or graft polymer. In other words, the ethyleneoxide group and propyleneoxide group or butyleneoxide group may be bonded in any of various forms.
In lubricating Oil VIII of the invention, the above mentioned component (B) is compounded so that the content of ethyleneoxide unit (C2H4O) may be 1 to 30% by weight, preferably 3 to 20% by weight of the total amount. If it is less than 1% by weight, the resulting oil becomes insufficient in antiwear property. If it is in excess of 30% by weight, troubles are caused in suitability to sealing materials, anti-peeling properties for coating material is lowered, and hygroscopicity increases undesirably. In addition, Lubricating Oil VIII loses its compatibility with fluorocarbon refrigerant containing no hydrogen such as R-12. Particularly, when the kinematic viscosity is high, the compatibility falls largely.
On the other hand, Lubricating Oil IX of the invention comprises main component (C) which is a compound having a kinematic viscosity at 100xc2x0 C. of 2 to 50 cSt and is represented by the general formula XVII:
CH3O(C2H4O)z(RO)wCH3xe2x80x83xe2x80x83XVII
wherein R indicates a propylene group or a butylene group, z and w are real numbers satisfying the requirements:
0.01xe2x89xa644z/Mxe2x80x2xe2x89xa60.3
in which Mxe2x80x2 is the molecular weight of the compound represented by the above formula and
5xe2x89xa6z+wxe2x89xa6100.
However, when w is a plural number, Rs may be identical to or different from each other. The main component (C) preferably has a kinematic viscosity of 5 to 30 cSt at 100xc2x0 C. Representative compounds represented by the general formula XVII include polyoxyethylene polyoxypropyleneglycol dimethylether, polyoxyethylene polyoxybutyleneglycol dimethylether, or polyoxyethylene polyoxypropylene polyoxybutyleneglycol dimethylether. Said component (C) is basically identical to the above-mentioned component (B), but the content of ethyleneoxide unit (C2H4O), that is, 44z/M, of component (C) must be 0.01 to 0.3, preferably 0.03 to 0.2.
In Lubricating Oil VIII of the invention, the proportion of the above-mentioned ethyleneoxide unit is controlled to be in the range of 1 to 30% by weight by compounding components (A) and (B), while in Lubricating Oil IX, the proportion of the ethyleneoxide unit is controlled in the prescribed range by the amount of the above-mentioned component (C).
Lubricating Oil VIII of the invention comprises the above-mentioned components (A) and (B) as the main components (or essential components), and Lubricating Oil IX comprises component (C) as the main component. Furthermore, various additives are used in the conventional lubricating oils, such as anti-load additives including extreme-pressure agents, antiwear agents, antioxidants, metal deactivating agents, defoaming agents, detergent dispersants, viscosity index improvers, rust inhibitors, anti-corrosion agents, pour point depressants, and further, mineral oils and synthetic oils to be used as the base oil for lubricating oils can be added, if necessary.
The present invention is described in greater detail with reference to the following examples.